OLED (Organic Light Emitting Diode) display, as a current-type light emitting device, is increasingly used in high-performance display fields due to its self-luminous, fast response, wide viewing angle, and ability to be fabricated on flexible substrates. According to the driving manner, the OLED can be classified into PMOLED (Passive Matrix Driving OLED) and AMOLED (Active Matrix Driving OLED). As the AMOLED display has the advantages of low manufacturing cost, high response speed, power saving, DC drive for portable equipment, wide operating temperature range and so on, the AMOLED display is expected to become a next-generation flat panel display replacing LCD (Liquid Crystal Display).
Existing OLED displays can use external compensation techniques to enhance display effect, such as obtaining drive current output by a driving transistor through a detection circuit and comparing it with the actual required reference current to achieve compensation. However, due to limitation of processes, many pixel defects may occur in the manufacturing process of the OLED display panel, and once a defect occurs in a certain sub-pixel, detection accuracy of other sub-pixels is also affected, which brings some difficulties to the compensation of the pixel, thus easily causing display abnormality.